This invention relates to an extension table suitable for use with a wide range of machine tools, which can easily be installed as needed to support long workpieces.
Stationary machine tools conventionally include at least one machine table, and there have been many attempts in the past to extend such machine tables. A number of previous approaches are illustrated in the following patents:
______________________________________ U.S.Pat. No. Inventor(s) ______________________________________ 1,583,879 Hallock 1,864,840 Lehner 2,555,217 Young 2,722,243 Nagy 3,406,728 Rost 4,068,551 Kreitz 4,106,381 Kreitz 4,248,115 Brodbeck, et al. 4,265,284 Taylor 4,341,247 Price 4,410,023 Vasquez 4,566,510 Bartlett, et al 4,627,478 Gamble 4,694,720 Brickner ______________________________________
The extension tables described by Young, Nagy, Dreitz, Rost, and Price are al secured to the edge of the machine table. Such edge connection does not automatically align the plane of the extension table with the plane of the machine table. For this reason an auxiliary alignment standard, such as a precision straightedge, must be used in order to install the extension table properly. The extension table shown in Brickner is a miter box that actually receives the miter saw. The extension tables or accessories shown in the Bartlett, Taylor, Vasquez, and Gamble patents are all secured to guide bars situated beneath the upper surface of the machine table. Similarly, the extension table shown in Hallock and the workpiece support shown in Lehner are mounted to the underside of the machine table. The Brodbeck sliding table is mounted via a linkage to the base of the machine tool.
These prior art extension tables, though effective for certain applications, all suffer from the disadvantage that they do not in any part extend above the surface of the machine table, and that they do not use the machine table surface as a reference plane to automatically align the extension table with the machine table. Furthermore, since these prior art extension tables mount on the edges, sides, or undersides of the machine tables or bases of the machine tools, the extension table must in each case be designed to accommodate the particular structure of the edge, side or underside of the machine table. In practice, machine tables differ widely in side and underside construction, and it is difficult or impossible to provide a universal mounting structure that will accommodate the wide variety of side and underside table structures in use.
A second characteristic of many prior art extension tables is that they are designed to support the workpiece symmetrically, either across the entire width of the workpiece or along its longitudinal center line. Such symmetrical workpiece support places further constraints on the design and structure of an extension table, constraints which interfere with convenient mounting of such extension tables on many machine tables.
Brodbeck shows in FIGS. 2 and 5 a fence extension 74 designed to telescope into the main fence 70 on the sliding table. This fence extension extends a short distance beyond the sliding table and includes a tab at its extreme end. The Brodbeck patent is assigned to Rockwell International Corporation, and the Rockwell Model 12 Panel/Scoring Saw resembles the saw shown in Brodbeck. Brochures for the Model 12 state that the fence extension helps support extra long stock.
The fence extension of Brodbeck is severely limited in application. First, it is cantilevered from a sliding table without free end support. This lack of support limits the effective length of the fence extension and places large demands on the stability of the machine tool. A heavy load on the fence extension tends to tip the machine tool. Since the fence extension must travel with the sliding table as the workpiece is cut, any support that contacts the floor is effectively eliminated. Second, the Brodbeck fence extension provides little more than point support to the workpiece. Such point support is completely inadequate for applications such as a jointer in which the workpiece is moved longitudinally along the support. On the infeed side, workpiece support provided by a tab such as that of Brodbeck will suddenly disappear as the trailing edge of the workpiece loses contact with the tab; on the outfeed side, the leading edge of the workpiece may sag and snag against the tab. Also the position of the tab must be adjusted for workpieces of varying lengths.
The present invention is directed to an improved extension table which can easily be mounted to almost any machine table and can readily be moved from one machine tool to another.
It is another object of this invention to provide such an extension table which automatically extends the plane of the machine table such that no auxiliary straight edge is required for proper alignment of the extension table, and which is adequately supported against deflection under load.
It is another object of this invention to provide such an extension table which maintains proper alignment with the machine table as the extension table is moved laterally across the machine table, or as the machine table is moved vertically.
It is yet another object of this invention to provide a self aligning extension table which provides continuous support to a workpiece as the workpiece slides on the extension table.